Process for preparing prepreg by continuous method

ABSTRACT

The present application relates to a process for preparing a prepreg by a continuous method, including the following steps: S1: preparing a raw material; S2: heating and stirring the raw material, and spinning in a spinning box to form a semi-finished ultra high molecular weight polyethylene fiber; S3: uniformly laying the semi-finished ultra high molecular weight polyethylene fiber into a layer, performing multistage drafting on the layer while immersing in a liquid matrix; S4: solidifying the matrix on the layer of ultra high molecular weight polyethylene fiber to form an ultra high molecular weight polyethylene fiber prepreg; S5: orthogonally aligning two sheets of the ultra high molecular weight polyethylene fiber prepregs with each other in warp and weft directions, and then performing lamination to form a weft-free fabric; and in step S3, performing multistage drafting by using a drafting device, and immersing by using an immersing device.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of PCT application serial no. PCT/CN2022/124360, filed on Oct. 10, 2022, which claims the priority and benefit of Chinese patent application serial no. 202111253574.6, filed on Oct. 27, 2021. The entireties of PCT application serial no. PCT/CN2022/124360 and Chinese patent application serial no. 202111253574.6 are hereby incorporated by reference herein and made a part of this specification.

TECHNICAL FIELD

The present application relates to a field of a fabric, in particular, to a process for preparing a prepreg by a continuous method.

BACKGROUND ART

An ultra high molecular weight polyethylene fiber, also known as a high strength and high modulus polyethylene fiber, is a fiber with a highest specific strength and specific modulus in the world at present. It is often used to make a bulletproof vest, a bulletproof helmet and a bulletproof armor of other military facilities and device.

A fabric made of the ultra high molecular weight polyethylene fiber is called as a weft-free fabric, and a preparation process in related technologies is as follows. After a raw material is prepared, the raw material is extruded into a spinning box by using a screw extruder. The raw material in the spinning box is ejected through a spinneret plate, heated and drafted, then evenly wound on a fabric reel. Then, the drafted ultra high molecular weight polyethylene fibers are uniformly laid into two layers in warp and weft directions, then the two layers of the fibers are bonded together by using a resin and pressed into a finished fabric.

For the related technologies described above, it is found that there are the following defects. During a process of winding the ultra high molecular weight polyethylene fiber on the fabric reel and pulling out from the fabric reel to make the weft-free fabric, a friction between the ultra high molecular weight polyethylene fibers may lead to an abrasion of the ultra high molecular weight polyethylene fibers, so that the uniformity of the ultra high molecular weight polyethylene fiber and a performance of the final finished fabric are reduced.

SUMMARY

In order to solve a problem of an abrasion caused by a friction between the ultra high molecular weight polyethylene fibers, the present application provides a process for preparing a prepreg by a continuous method.

The process for preparing the prepreg by the continuous method provided in the present application adopts the following technical solutions.

The process for preparing the prepreg by the continuous method includes the following steps:

S1: a raw material is prepared;

S2: the raw material is heated and stirred, and then fed into a spinning box for spinning to form a semi-finished ultra high molecular weight polyethylene fiber;

S3: the semi-finished ultra high molecular weight polyethylene fiber is uniformly laid, and multistage drafted when being immersed in a liquid matrix to obtain a finished product;

S4: a matrix on an ultra high molecular weight polyethylene fiber layer is solidified to form an ultra high molecular weight polyethylene fiber prepreg;

S5: two sheets of ultra high molecular weight polyethylene fiber prepregs are orthogonally aligned with each other in warp and weft directions, and then laminated to form a weft-free fabric; and

in step S3, the semi-finished ultra high molecular weight polyethylene fiber is multistage drafted by using a drafting device, and the ultra high molecular weight polyethylene fiber layer is immersed by using an immersing device.

In the above technical solutions, the semi-finished ultra high molecular weight polyethylene fiber is multistage drafted when being immersed in the liquid matrix to obtain the finished product; the finished ultra high molecular weight polyethylene fiber is prepared into the prepreg and stored; and finally two sheets of ultra high molecular weight polyethylene fiber prepregs are orthogonally aligned with each other in warp and weft directions, and then laminated to form a weft-free fabric. The ultra high molecular weight polyethylene fiber is stored as the prepreg, so that the ultra high molecular weight polyethylene fiber is less prone to damage caused by the mutual friction when being stored and used, thus a quality of the final weft-free fabric was improved.

In some embodiments, the drafting device includes a frame, the frame is rotatably provided with a plurality of drafting rollers parallel to each other, and provided with a plurality of drive motors with a same number as the drafting rollers; the drive motors are one-to-one connected with the drafting rollers in a transmission way; and the frame is provided with a finishing assembly configured for finishing and laying a fiber.

In the above technical solutions, after the semi-finished fiber is transported to the frame, the drive motor are started synchronously. At the same time, rotation speeds of the drive motors are adjusted in sequence along a fiber transportation direction to make the rotation speeds of the drive motors increase sequentially along the fiber transportation direction, so that rotation speeds of the drafting rollers are increased sequentially to draft the fibers. When the semi-finished fiber is drafted by using the drafting rollers, a fiber after being drafted is finished by using the finishing assembly, so that a distribution of the fibers is relatively uniform when transported to the immersing device for being immersed in the matrix. Thus, a strength of each part of the final formed prepreg is relatively uniform.

In some embodiments, the finishing assembly includes a mounting frame provided at an outlet end of the frame, and an inlet end of the mounting frame is provided with a pair of driving rollers; two ends of the two driving rollers departing from each other are rotatably connected with the mounting frame, and two ends of the two driving rollers facing each other extends obliquely in a same direction; rubber roller is provided between the two driving rollers, and each end of the rubber roller is coaxially defined with a connection hole; two ends of the two driving rollers facing each other are embedded in two connection holes respectively; an axis of the rubber roller is vertical to a transportation direction of the frame; an outlet end of the mounting frame is rotatably provided with two horizontal pressing rollers parallel to each other, and an axis of each of the pressing rollers is vertical to the transportation direction of the frame; the mounting frame is provided with two first finishing motors respectively connected with the two driving rollers in the transmission way; and the mounting frame further is provided with a second finishing motor connected with one end of any one of the pressing rollers.

In the above technical solutions, after being output from a last drafting roller, the semi-finished fiber is transported around the two rubber rollers driven to rotate by the two inclined driving roller. After a loose finished fiber bundle are gathered by the curved rubber rollers, the gathered finished fiber bundle is constrained to be a uniform layer by the two pressing roller, and then a fiber layer is immersed in the matrix. By using the curved rubber rollers to gather and constrain the finished fibers, the fibers are uniformly distributed when being gathered together.

In some embodiments, the mounting frame is rotatably provided with two first mounting blocks, and rotating planes thereof are parallel to a plane where axes of the two driving rollers are located; the two driving rollers are rotatably provided on the two first mounting blocks respectively, and the first finishing motors are provided on the first mounting blocks respectively; the mounting frame is vertically slidably provide with two second mounting blocks, and both ends of any one of the pressing rollers are respectively rotatably connected with the two second mounting blocks; and the mounting frame is provided with a first fixing part for fixing the first mounting blocks and a second fixing part for fixing the second mounting blocks.

In the above technical solutions, thicknesses required for the final fabrics varies, and thicknesses required for the prepregs also varies. When preparing the prepreg, an aggregation degree and thickness of the finished fibers are adjusted by adjusting a bending degree of the rubber roller by rotating the first mounting block to achieve the thickness required for the prepreg.

In some embodiments, the first fixing part includes a worm rotatably provided on the mounting frame, and thread rotation directions of both ends of the worm are opposite; each of the two first mounting blocks is coaxially provided with a worm gear, and the two worm gears are respectively engaged with both ends of the worm; one end of the worm is coaxially provided with a hand wheel with a pointer, and the mounting frame is provided with a scale coaxial with an axis of the hand wheel and configured for coordinating with the pointer; the second fixing part includes a vertical gear rack provided on any one of the second mounting blocks; and the mounting frame is rotatably provided with a transmission gear engaged with gear rack and connected with the worm in the transmission way.

In the above technical solutions, a user can easily rotate the worm by using the hand wheel, and then the worm gear and the first mounting block are driven to rotate by the worm. The first mounting block is fixed by a self-locking function between the worm and the worm gear, meanwhile the gear rack and the second mounting block are adjusted and fixed by the transmission gear connected with the worm in the transmission way. Therefore, a distance between the two pressing roller can be adjusted when the user adjust the bending degree of the rubber roller, which allows the user to easily adjust the distance between the two pressing rollers to an extent that they match with the rubber rollers. Meanwhile, the bending degree of the rubber roller can be determined more intuitively through a coordination between the pointer on the hand wheel and the scale.

In some embodiments, the immersing device includes a support provided at an outlet end of the frame; the support is vertically slidably provide with a hopper, and a heating part is provided in the hopper; the hopper is provided with a positioning part configured for fixing the hopper on the support; a bottom wall of the hopper is provided with a flat discharge pipe, and an end thereof is in communication with an inner cavity of the hopper; the discharge pipe is rotatably provided with a horizontal first material roller, the support below the hopper is provided with a recovery box, and a vertical projections of the discharge pipe is located in the recovery box; a second material roller is rotatably provided in the recovery box, and an upper side of the second material roller is higher than a side wall of the recovery box; the second material roller is located directly below the first material roller; and a recovery pump is provided in the recovery box, and an outlet end of the recovery pump is in communication with the inner cavity of the hopper through a pipe.

In the above technical solutions, the heating part heats the matrix in the hopper to maintain a constant temperature, so that the matrix in the hopper is not easy to be solidified. The fiber layer is transported to a position between the discharge pipe and the first material roller after being finished by the rubber roller and the pressing roller. The matrix in the hopper is applied onto the fiber layer through the discharge pipe. Then, the fiber layer and a matrix layer are pressed through a coordination between the first material roller and the second material roller, so that the matrix layer is evenly wrapped around the fiber layer, and then the matrix immersing of the fiber layer is completed. An excess matrix will fall into the recovery box and be pumped back into the hopper by the recovery pump of the recovery box for reuse.

In some embodiments, a lower end of the discharge pipe bends towards an opposite direction of a fiber transportation direction of the frame.

In the above technical solutions, when the liquid matrix is transported onto the fiber layer by the curved discharge pipe, an impact force of the liquid matrix falling onto the fiber layer is relatively small, so that a vibration of the fiber layer is reduced, and the matrix on the fiber layer is not easy to be thrown off the fiber layer due to the vibration of the fiber layer

In some embodiments, a horizontal closing roller is rotatably provided in the hopper, and a side wall of the hopper is provided with a closing motor connected with the closing roller in the transmission way; a side wall of the closing roller is provided a plurality of closing plates arranged along a circumferential direction at intervals, and the bottom wall of the hopper is provided with closing groove, which is in communication with the discharge pipe; and a lower side of the closing roller is located in the closing groove, and a side wall of the closing plate abuts against a side wall of the closing groove.

In the above technical solutions, the closing motor is started to drive the closing roller to rotate, and further the closing plate is driven to rotate to stir the liquid matrix in the hopper to make the liquid matrix in the hopper more uniform. Meanwhile, a pressure is provided to the liquid matrix in the discharge pipe by the closing plate, so that the liquid matrix is not easy to be blocked in the discharge pipe. At the same time, the hopper is closed by a coordination between the closing plate and the closing groove, and a closing of the hopper is more convenient.

In some embodiments, bottom walls of the hopper and the recovery box are funnel-shaped.

In the above technical solutions, the liquid matrix flows more quickly at the bottom walls of funnel-shaped hopper and the recovery box, so that the matrix is not easy to be deposited on the bottom walls of the hopper and the recovery box. Thus, interiors of the hopper and the recovery box are relatively clean, which is less likely to pollute a new matrix.

In some embodiments, a side wall of each of the driving roller is provided with a plurality of positioning plates arranged along the circumferential direction at intervals, and a side wall of each of the connection holes is defined with a plurality of positioning grooves arranged along the circumferential direction at intervals, which are in one-to-one correspondence with the positioning plates, and the positioning plates are slidably provided in the positioning grooves respectively.

In the above technical solutions, by a coordination between the positioning plate and the positioning groove, when the driving roller drives the rubber roller to rotate, the driving roller is not prone to sliding relative to the rubber roller, and a rotation of the rubber roller is more stable.

In summary, the present application has at least one of the following beneficial technical effects:

-   -   1. the semi-finished ultra high molecular weight polyethylene         fiber is multistage drafted when being immersed in the liquid         matrix to obtain the finished product; the finished ultra high         molecular weight polyethylene fiber is prepared into the prepreg         and stored; and finally two sheets of ultra high molecular         weight polyethylene fiber prepregs are orthogonally aligned with         each other in warp and weft directions, and then laminated to         form a weft-free fabric. The ultra high molecular weight         polyethylene fiber is stored as the prepreg, so that the ultra         high molecular weight polyethylene fiber is less prone to damage         caused by the mutual friction when being stored and used, thus a         quality of the final weft-free fabric was improved;     -   2. after being output from a last drafting roller, the         semi-finished fiber is transported around the two rubber rollers         driven to rotate by the two inclined driving roller. After a         loose finished fiber bundle are gathered by the curved rubber         rollers, the gathered finished fiber bundle is constrained to be         a uniform layer by the two pressing roller, and then a fiber         layer is immersed in the matrix. By using the curved rubber         rollers to gather and constrain the finished fibers, the fibers         are uniformly distributed when being gathered together; and     -   3. the closing motor is started to drive the closing roller to         rotate, and further the closing plate is driven to rotate to         stir the liquid matrix in the hopper to make the liquid matrix         in the hopper more uniform. Meanwhile, a pressure is provided to         the liquid matrix in the discharge pipe by the closing plate, so         that the liquid matrix is not easy to be blocked in the         discharge pipe. At the same time, the hopper is closed by a         coordination between the closing plate and the closing groove,         and the closing of the hopper is more convenient.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a three-dimensional structure of the present application.

FIG. 2 is the diagram of the three-dimensional structure of the present application, in which some parts of a frame is excluded and a rubber roller is section cut.

FIG. 3 is an enlarged diagram of part A in FIG. 2 .

FIG. 4 is the diagram of the three-dimensional structure of a second mounting block in the present application.

FIG. 5 is a cross-sectional diagram of a hopper and a recovery box of the present application, without the support.

DETAILED DESCRIPTION

The present application is further described in detail below in combination with FIGS. 1-5 .

EXAMPLES Example 1

Example 1 of the present application disclosed a process for preparing a prepreg by a continuous method includes the following steps:

-   -   S1 preparing a raw material: 1 kg of an ultra high molecular         weight polyethylene resin with an weight-average molecular         weight of 1.8 million were added into 9 kg of a         decahydronaphthalene solvent, and then the raw material was         obtained;     -   S2: the raw material obtained in step S1 was heated, stirred and         swelled, and was fed into a spinning box by using a screw         extruder; and then, semi-finished ultra high molecular weight         polyethylene fibers were formed by spinning; a swelling         temperature was 100° C. and a swelling time was 1 h;     -   S3: the semi-finished ultra high molecular weight polyethylene         fibers obtained in step     -   S2 were uniformly laid, and multistage drafted when being         immersed in a liquid matrix, so that a finished product was         obtained;

S4: a matrix on an ultra high molecular weight polyethylene fiber layer was solidified, so that an ultra high molecular weight polyethylene fiber prepreg was formed;

-   -   S5: two sheets of the ultra high molecular weight polyethylene         fiber prepregs were aligned orthogonally with each other in warp         and weft directions, and then a weft-free fabric was formed         after lamination.

In particular, in step S3, the liquid matrix was made of 1.5 kg resorcinol, 2.8 kg formaldehyde, 0.05 kg sodium hydroxide, 0.43 kg rubber emulsion, 1.7 kg aqueous ammonia and 0.50 kg deionized water, and was prepared by the following steps:

-   -   (1) 40% of total amount of deionized water was added into the         container, sodium hydroxide was added and stirred, and         resorcinol was added and stirred until it dissolved; then,         formaldehyde was added, stirred for 5 min and aged at 20° C. for         2 h;     -   (2) 10% of total amount of deionized water was added into a         final preparation container, so that the rubber emulsion was         diluted;     -   (3) a solution after being aged in step (1) was added into a         diluted rubber emulsion in step (2), and stirred for 15 min;     -   (4) aqueous ammonia was added and stirred for 10 min;     -   (5) a preparation solution was aged at a room temperature for 17         h.

Referring to FIG. 1 , in step S3, the semi-finished ultra high molecular weight polyethylene fibers were multistage drafted by using a drafting device 1. The drafting device 1 includes a vertical plate-shaped frame 11, a vertical surface thereof is rotatably connected with a plurality of horizontal drafting rollers 12, and all of the drafting rollers 12 are parallel to each other. The frame 11 is fixedly mounted with a plurality of drive motors 13 corresponding to a plurality of drafting rollers 12, and an output shaft of each of the drive motors 13 is coaxially fixed with an end of the drafting roller 12 rotatably connected to the frame 11.

Referring to FIG. 2 and FIG. 3 , the frame 11 is provided with a finishing assembly 2, including a mounting frame 2 fixedly mounted at an outlet end of the frame 11. An end of the mounting frame 2 close to the frame 11 is rotatably connected with two first mounting blocks 25. Rotating planes of the two first mounting blocks 25 are vertical and overlap, and vertical to a fiber transportation direction of the frame 11. The mounting frame 21 is provided with a first fixing part 3 including a worm gear 32 fixedly mounted on the first mounting block 25, and the worm gear 32 is coaxial with a rotating axis of a first mounting block 25 where the worm gear 32 is located. The frame 11 is rotatably mounted with a horizontal worm 31, and thread rotation directions of both ends of the horizontal worm 31 are opposite. Both ends of the worm 31 are respectively engaged with the two worm gears 32. The worm 31 rotates to drive the two worm gears 32 and the two mounting blocks to rotate reversely.

Referring to FIG. 2 and FIG. 3 , one end of the worm 31 passes through the mounting frame 21 and is coaxially fixed with a hand wheel 33. The hand wheel 33 is fixedly mounted with a pointer 34, and the mounting frame 21 is provided with a scale 35 configured for coordinating with the pointer 34.

Referring to FIG. 3 and FIG. 4 , each of the first mounting blocks 25 is rotatably mounted with one driving roller 22 and fixedly mounted with one first finishing motor 251. An output shaft of the first finishing motor 251 is fixedly connected with one end of the driving roller 22. A rotating plane of the driving roller 22 is parallel to the rotating plane of the first mounting block 25, and a side wall at an end of the driving roller 22 away from the first mounting block 25 is welded with six rectangular positioning plates 221 along a circumferential direction at intervals. A rubber roller 23 is provided between the two driving rollers 22, and each of both end surfaces of the rubber roller 23 is coaxially defined with a connection hole 231 configured for coordinating with the driving roller 22. A side wall of the connection hole 231 is defined with six positioning grooves 232 arranged along the circumferential direction at intervals, which are configured for coordinating with the positioning plates 221. Two ends of the two driving rollers 22 facing each other are slidably mounted in the two connection holes 231 respectively, and the positioning plates 221 are slidably mounted in the six positioning grooves 232 respectively.

Referring to FIG. 3 and FIG. 4 , a bending degree of the rubber roller 23 is adjusted by rotating the first mounting block 25, and the driving roller 22 and rubber roller 23 are not easy to slide relative to each other because of a coordination of the positioning plate 221 and the positioning groove 232. An end of the mounting frame 21 away from the frame 11 is rotatably mounted with one horizontal pressing roller 24, and an axis of the pressing roller 24 is vertical to the fiber transportation direction of frame 11.

Referring to FIG. 3 and FIG. 4 , another one pressing roller 24 is provided directly below the pressing roller 24, and the two pressing rollers 24 are parallel to each other. A part of the mounting frame 32 where each of both ends of the pressing roller 24 is located is vertically slidably mounted with one second mounting block 26, and both ends of the pressing roller 24 located at a lower side is rotatably mounted on the two second mounting blocks 26 respectively.

Referring to FIG. 3 and FIG. 4 , an axis of the pressing roller 24 is parallel to an axis of the drafting roller 12. The second mounting block 26 located at a freed end of the drafting roller 12 is fixedly mounted with the second finishing motor 261, and an output shaft thereof is coaxially fixed with the pressing roller 24 located at the lower side.

Referring to FIG. 3 and FIG. 4 , the mounting frame 21 is provided with a second fixing part 4 including one gear rack 41 and one transmission gear 42. The gear rack 41 is vertical and welded on the second mounting block 26 mounted with the second finishing motor 261. The transmission gear 42 is rotatably mounted on the mounting frame 21 and engaged with gear rack 41, and is connected with the worm 31 in a transmission way by a bevel gear 7. By the transmission gear 42 connected with the worm 31 in the transmission way, when the first mounting block 25 rotates, the second mounting block 26 synchronously slides.

Referring to FIG. 2 and FIG. 5 , in step S3, the ultra high molecular weight polyethylene fiber layer is immersed in a matrix by using an immersing device 5. The immersing device 5 includes a support 51 fixedly mounted on the end of the mounting frame 21 away from the frame 11. The support 51 is provided with a fixing part, including a vertical polish rod 532 fixedly mounted on the support 51 and a vertical screw rod 531 rotatably mounted on the support 51. The support 51 is provided with a hopper 52 with a funnel-shaped bottom, and an upper opening of the hopper 52 is horizontal. The polish rod 532 passes through and is slidably connected with the hopper 52, and the screw rod 531 passes through and is in threaded connection with the hopper 52. The hopper 52 is slidably mounted on the support 51 through a coordination of the polish rod 532 and the screw rod 531, and is fixed by the screw rod 531.

Referring to FIG. 2 and FIG. 5 , a horizontal closing roller 6 is rotatably mounted in the hopper 52, and a heating part also is provided in the hopper. The heating part includes two heating rod 521 fixedly mounted at a side wall of the hopper 52. The side wall of the hopper 52 is fixedly mounted with a closing motor 61, an output shaft thereof is coaxially fixed with an end of the closing roller 6, and an axis thereof is parallel to the axis of the pressing roller 24. A side wall of the closing roller 6 is integrally formed with a plurality of rectangular closing plates 62 arranged along the circumferential direction at intervals, and a length direction of the rectangular closing plate 62 is parallel to the axis of the closing roller 6. A bottom wall of the hopper 52 is defined with a closing groove 522 with a curved cross section. A lower side of the closing roller 6 is located in the closing groove 522, and a side wall of the closing plate 62 away from the closing roller 6 abuts against a side wall of the closing groove 522. The bottom wall of the hopper 52 is integrally formed with an discharge pipe 54, and a cross section thereof is rectangular. A lower end of the discharge pipe 54 bends towards the mounting frame 21. A side wall of the discharge pipe 54 further is rotatably mounted with a first material roller 55 parallel to the closing roller 6, and the discharge pipe 54 is in communication with an inner cavity of the closing groove 522.

Referring to FIG. 2 and FIG. 5 , the support 51 located directly below the hopper 52 is fixedly mounted with a recovery box 56 with the funnel-shaped bottom. Vertical projections of the discharge pipe 54 and the first material roller 55 are located in the recovery box 56. A second material roller 561 is rotatably mounted in the recovery box 56, and is located directly below the first material roller 55. An upper side of the second material roller 561 extends out of the recovery box 56. The fiber layer passes through a space between the first material roller 55 and the second material roller 561, and the liquid matrix flows out of the discharge pipe 54 and then falls on the fiber layer. The liquid matrix is squeezed in the fiber layer by using the first material roller 55 and the second material roller 561.

Referring to FIG. 2 and FIG. 5 , a bottom wall of the recovery box 56 is fixedly mounted with a recovery pump 562. An inlet end of the recovery pump 562 is in communication with an inner cavity of the recovery box 56 through a pipe, and an outlet end of the recovery pump 562 transports an excess matrix in the recovery box 56 back to the hopper 52 through a water pipe.

An implementation principle of the process for preparing the prepreg by the continuous method in the embodiment of this present application is as follows. The drive motor 13 is started, and then the semi-finished ultra high molecular weight polyethylene fibers are input to the frame 11. The semi-finished ultra high molecular weight polyethylene fibers are drafted by using the drafting roller 12 to form the finished ultra high molecular weight polyethylene fibers, which are input to the mounting frame 21 and passed around the rubber roller 23. The first finishing motor 251 is started to drive the rubber roller 23 to rotate by the driving roller 22, and the rubber roller 23 uniformly gathers together the ultra high molecular weight polyethylene fiber layer and then inputs it to a space between two pressing rollers 24. The second finishing motor 251 is started to drive the pressing roller 24 located at the lower side to rotate, and the two pressing rollers 24 flatten a curved ultra high molecular weight polyethylene fiber layer and transport it to the support 51. The ultra high molecular weight polyethylene fiber layer passes through the space between the first material roller 55 and the second material roller 561, and then is output. When the ultra high molecular weight polyethylene fiber layer passes through the space between the first material roller 55 and the second material roller 561, the closing motor 61 is started to drive the closing roller 6 to rotate, and the liquid matrix in the hopper 52 is discharged from the discharge pipe 54 and then is applied on the fiber layer by the closing roller 6. After the matrix is squeezed in the fiber layer and the fiber layer is output by using the first material roller 55 and the second material roller 561, the liquid matrix is solidified to form the ultra high molecular weight polyethylene fiber prepreg.

A user rotates the hand wheel 33 to drive the worm 31 to rotate, and further the worm gear 32 and the first mounting block 25 are driven to rotate to adjust the bending degree of the rubber roller 23, and the transmission gear 42 is driven to rotate by the bevel gear 7. Thus, heights of the second mounting block 26 and the pressing roller 24 are adjusted, and heights of the hopper 52 and the first material roller 55 are adjusted by rotating the screw rod 531.

Example 2

This example differs from Example 1 in that: in step S1, 2 kg of the ultra high molecular weight polyethylene resin with the weight-average molecular weight of 1.8 million were added into 8 kg of the decahydronaphthalene solvent, and then the raw material was obtained.

Example 3

This example differs from Example 1 in that: in step S1, 3 kg of the ultra high molecular weight polyethylene resin with the weight-average molecular weight of 1.8 million were added into 7 kg of the decahydronaphthalene solvent, and then the raw material was obtained.

Example 4

This example differs from Example 1 in that: in step S1, the weight-average molecular weight of the ultra high molecular weight polyethylene resin was 2 million.

COMPARATIVE EXAMPLES

Comparative Example 1

The process for preparing the weft-free fabric includes the following steps:

S1 preparing the raw material:

1 kg of the ultra high molecular weight polyethylene resin with the weight-average molecular weight of 1.8 million were added into 9 kg of a decahydronaphthalene solvent, and then the raw material was obtained;

S2: the raw material obtained in step S1 was heated, stirred and swelled, and was fed into the spinning box by using the screw extruder; and then, the semi-finished ultra high molecular weight polyethylene fibers were formed by spinning; the swelling temperature was 100° C. and the swelling time was 1 h;

S3: the semi-finished ultra high molecular weight polyethylene fibers obtained in step S2 were uniformly laid, and after being multistage drafted, the finished product was obtained;

S4: two sheets of the ultra-high molecular weight polyethylene fibers were aligned orthogonally with each other in warp and weft directions, and were laminated by using a resin, and finally the weft-free fabric was formed.

In particular, in step S3, the semi-finished ultra high molecular weight polyethylene fiber was multistage drafted by using the drafting device 1.

Comparative Example 2

This comparative example differs from Comparative Example 1 in that: in step S3, the semi-finished ultra high molecular weight polyethylene fibers were multistage drafted by using a commonly used multi roller drafting machine on the market.

Performance Test

The weft-free fabrics prepared by the examples and the comparative examples were cut into multiple 400 mm*400 mm square target pieces, which were divided into 3 portions. After 28 layers were stacked for each portion, a shooting test was conducted according to the NIJ0101.06 MA level. A concavity performance of each sample in each example and comparative example was shown in Table 1.

TABLE 1 concavity Average concavity Examples performance/mm performance/mm Example 1 Sample 1 28 27.7 Sample 2 27 Sample 3 28 Example 2 Sample 1 29 29 Sample 2 29 Sample 3 29 Example 3 Sample 1 28 28 Sample 2 28 Sample 3 28 Example 4 Sample 1 25 25 Sample 2 25 Sample 3 25 Comparative Sample 1 34 33.7 Example 1 Sample 2 31 Sample 3 36 Comparative Sample 1 37 36.7 Example 2 Sample 2 43 Sample 3 30

In combination with examples 1-4, comparative example 1 and table 1, it can be seen that, the concavity performance of each sample of the weft-free fabric prepared in examples 1-4 was relatively uniform compared to comparative example 1. That was, the weft-free fabric prepared by using the ultra high molecular weight polyethylene fiber that was prepared after being immersed in the liquid matrix had a uniform strength in various parts. That was, a fiber distribution was relatively uniform. This was because during storage and use, the ultra high molecular weight polyethylene fibers prepared after being immersed in the liquid matrix were less prone to damage caused by the friction, thus a quality of the final weft-free fabric was improved.

In combination with comparative examples 1-2 and table 1, it can be seen that, the concavity performance of each sample of the weft-free fabric prepared in comparative example 1 was relatively uniform compared to comparative example 2. That was, compared with the weft-free prepared by using the commercially available multi roller drafting machine, the weft-free fabric prepared by using the drafting device provided in the present application has a uniform strength, that was, the fiber distribution was more uniform.

In combination with examples 1-3 and table 1, it can be seen that, the concavity performance of the weft-free fabric prepared in examples 1-3 was almost the same, which indicated that changing a weight ratio of the ultra high molecular weight polyethylene resin to decahydronaphthalene has a little effect on a depression degree of the finished weft-free fabric.

In combination with examples 1, 4 and table 1, it can be seen that, the concavity performance of the weft-free fabric prepared in example 4 was better than example 1. This was because that, the weight-average molecular weight of the ultra high molecular weight polyethylene resin used in Example 4 was 2 million, but the weight-average molecular weight of the ultra high molecular weight polyethylene resin used in Example 1 was 1.8 million. The higher the weight-average molecular weight of the ultra high molecular weight polyethylene resin, the higher its abrasion resistance and impact resistance.

The above are the preferred embodiments of the present application, which are not intended to limit the protection scope of the present application. Therefore, all equivalent changes made according to the structure, shape and principle of the present application should be covered within the protection scope of the present application.

LISTING OF REFERENCE SIGNS

-   -   1. drafting device     -   11. frame     -   12. drafting roller     -   13. drive motor     -   2. finishing assembly     -   21. mounting frame     -   22. driving roller     -   221. positioning plate     -   23. rubber roller     -   231. connection hole     -   232. positioning groove     -   24. pressing roller     -   25. first mounting block     -   251. first finishing motor     -   26. second mounting block     -   261. second finishing motor     -   3. first fixing part     -   31. worm     -   32. worm gear     -   33. hand wheel     -   34. pointer     -   35. scale     -   4. second fixing part     -   41. gear rack     -   42. transmission gear     -   5. immersing device     -   51. support     -   52. hopper     -   521. heating rod     -   522. closing groove     -   20 53. positioning part     -   531. screw rod     -   532. polish rod     -   54. discharge pipe     -   55. first material roller     -   56. recovery box     -   561. second material roller     -   562. recovery pump     -   6. closing roller     -   61. closing motor     -   62. closing plate     -   7. bevel gear 

What is claimed is:
 1. A process for preparing a prepreg by a continuous method comprising the following steps: step S1: preparing a raw material; step S2: heating and stirring the raw material, and spinning in a spinning box to form a semi-finished ultra high molecular weight polyethylene fiber; step S3: uniformly laying the semi-finished ultra high molecular weight polyethylene fiber into a layer, performing multistage drafting on the layer while immersing in a liquid matrix; step S4: solidifying the liquid matrix on the layer of ultra high molecular weight polyethylene fiber to form an ultra high molecular weight polyethylene fiber prepreg; and step S5: orthogonally aligning two sheets of the ultra high molecular weight polyethylene fiber prepregs with each other in warp and weft directions, and then performing lamination to form a weft-free fabric.
 2. The process for preparing the prepreg by the continuous method according to claim 1, wherein, the multistage drafting is performed on a drafting device, and the drafting device comprises a frame rotatably provided with a plurality of drafting rollers parallel to each other, provided with a plurality of drive motors in a same number as that of the drafting rollers and one-to-one connected with the drafting rollers in a transmission way, and provided with a finishing assembly configured for finishing and laying a fiber.
 3. The process for preparing the prepreg by the continuous method according to claim 2, wherein, the finishing assembly comprises a mounting frame provided at an outlet end of the frame, and an inlet end of the mounting frame is provided with a pair of driving rollers; two ends of the pair of driving rollers departing from each other are rotatably connected with the mounting frame, and two ends of the pair of driving rollers facing each other extend obliquely in a same direction; a rubber roller is provided between the pair of driving rollers, and each end of the rubber roller is coaxially defined with a connection hole; two ends of the pair of driving rollers facing each other are inserted in two connection holes respectively; an axis of the rubber roller is vertical to a transportation direction of the frame; an outlet end of the mounting frame is rotatably provided with two horizontal pressing rollers parallel to each other, and an axis of each of the two horizontal pressing rollers is vertical to a fiber transportation direction of the frame; the mounting frame is provided with two first finishing motors respectively connected with the pair of driving rollers in the transmission way; and the mounting frame further is provided with a second finishing motor connected with one end of one of the two horizontal pressing rollers.
 4. The process for preparing the prepreg by the continuous method according to claim 3, wherein, the mounting frame is rotatably provided with two first mounting blocks, and rotating planes of the two first mounting blocks are parallel to a plane where axes of the pair of driving rollers are located; the pair of driving rollers are rotatably provided on the two first mounting blocks respectively, and the two first finishing motors are provided on the two first mounting blocks respectively; the mounting frame is vertically slidably provided with two second mounting blocks, and both ends of one of the two horizontal pressing rollers are respectively rotatably connected with the two second mounting blocks; and the mounting frame is provided with a first fixing part for fixing the two first mounting blocks and a second fixing part for fixing the two second mounting blocks.
 5. The process for preparing the prepreg by the continuous method according to claim 4, wherein, the first fixing part comprises a worm rotatably provided on the mounting frame and having reverse thread directions at two ends of the worm; each of the two first mounting blocks is coaxially provided with a worm gear, and the two worm gears are respectively engaged with both ends of the worm; one end of the worm is coaxially provided with a hand wheel with a pointer, and the mounting frame is provided with a scale coaxial with an axis of the hand wheel and in cooperation with the pointer; the second fixing part comprises a vertical gear rack provided on any one of the two second mounting blocks; and the mounting frame is rotatably provided with a transmission gear engaged with vertical gear rack and transmission connected with the worm.
 6. The process for preparing the prepreg by the continuous method according to claim 2, wherein, the immersing in step S3 is performed in an immersing device, and the immersing device comprises a support provided at an outlet end of the frame; the support is vertically slidably provide with a hopper, and a heating part is provided in the hopper; the hopper is provided with a positioning part configured for fixing the hopper on the support; a bottom wall of the hopper is provided with a flat discharge pipe, and an end of the flat discharge pipe is in communication with an inner cavity of the hopper; the flat discharge pipe is rotatably provided with a horizontal first material roller, the support below the hopper is provided with a recovery box, and a vertical projection of the flat discharge pipe is located in the recovery box; a second material roller is rotatably provided in the recovery box, and an upper side of the second material roller is higher than a side wall of the recovery box; the second material roller is located directly below the horizontal first material roller; and a recovery pump is provided in the recovery box, and an outlet end of the recovery pump is in communication with the inner cavity of the hopper through a pipe.
 7. The process for preparing the prepreg by the continuous method according to claim 6, wherein, a lower end of the flat discharge pipe bends towards a direction opposite to a fiber transportation direction of the frame.
 8. The process for preparing the prepreg by the continuous method according to claim 6, wherein, a horizontal closing roller is rotatably provided in the hopper, and a side wall of the hopper is provided with a closing motor connected with the horizontal closing roller in the transmission way; a side wall of the horizontal closing roller is circumferentially provided with a plurality of closing plates at intervals, and the bottom wall of the hopper is provided with a closing groove in communication with the flat discharge pipe; and a lower side of the horizontal closing roller is located in the closing groove, and a side wall of each of the closing plates abuts against a side wall of the closing groove.
 9. The process for preparing the prepreg by the continuous method according to claim 6, wherein, the hopper and the recovery box have funnel-shaped bottom walls.
 10. The process for preparing the prepreg by the continuous method according to claim 3, wherein, a side wall of each of the pair of driving roller is circumferentially provided with a plurality of positioning plates at intervals, and a side wall of each of the two connection holes is circumferentially defined with a plurality of positioning grooves at intervals, the positioning grooves are in one-to-one correspondence with the positioning plates, and the positioning plates are one-to-one slidably provided in the positioning grooves. 